The invention relates to photoelectric pulse initiators for pulse operated meter telemetry and recording systems and more particularly to such pulse initiators including a low power digital I.C. arrangement for simplifying and controlling the transmitted pulses generated by the pulse initiator and to afford a simplified recording apparatus receiving the transmitted pulses.
In U.S. Pat. No. 3,733,493 issued May 15, 1973 to T. M. McClelland III and in U.S. Pat. No. 3,878,391 issued Apr. 15, 1975 to T. M. McClelland III et al., both assigned to the assignee of this invention, radiation or photoelectric pulse initiators are disclosed for use in the electric power metering field for initiating meter data pulses in response to the rate of rotation of a utility meter of the watthour type. In these prior systems various techniques are described for generating pulses in response to the meter rotation with an output pulse generator formed by a latching type three-wire contact device such as a mercury wetted relay. Large current values are sometimes required to adequately operate the relay in extremely cold environments and are typically inefficient. Since the relay effectively isolates the pulse initiator output and a data receiving recording circuit, separate power supply sources are required to supply both the pulse initiator circuits and the data recording circuits. Mechanical control for varying the pulse rate in response to the speed of the meter shaft movement, referred to as the constant Mp in the above-identified application, is not always satisfactory for all applications. Gear train ratios used in driving a patterned disk or drum in the pulse initiator mechanism or the number of reflective segments forming the indicia of the pulse initiator pattern often require substantial interchanging of parts and have limitations due to undesired loading of the meter shaft and space available within the meter housing. Ratios of less than one pulse per meter shaft rotation are often only possible by changing a gear train ratio while high output pulse numbers per shaft rotation are often only obtainable by increasing the number of reflective segments in the shaft driven pattern.
In the data magnetic recording systems used in utility meter recording telemetry systems it has been noted that watthour meter shaft speeds may reach as high as 6,670 revolutions per hour so that with two reflective segments over 13,000 pulses per hour might be produced from a pulse initiator while the data pulse receiver including a magnetic recorder may be capable of handling only 7,000 pulses per hour. This requires that the number of pulses developed at the radiation pickup sensors be divided to a lower rate proportional to the meter shaft speed.
Accordingly, it is desirable to simplify the components and numbers of components required to initiate and record meter data pulses in pulse initiators used in metering telemetry systems, to improve the reliability and adverse operating characteristics due to mechanical parts, to decrease power required in such telemetry systems, and to add greater flexibility in controlling the output pulse rates of pulse initiators to provide different desired pulse rates relative to a given watthour meter shaft rotation. In consideration of the aforementioned deficiencies and undesirable aspects in prior art devices the present invention is made as briefly summarized hereinafter.